When Johnny Carson announced his retirement, he promised the Tonight Show to David Letterman. However, NBC gave it to Jay Leno instead, resulting in a long time feud between the two. According to the book "The Late Shift", Carson felt betrayed by NBC and Leno. Carson stayed friends with Letterman until his death.

The The Tonight Show Starring Johnny Carson (1962)'s previous host, Johnny Carson, never once appeared on successor Jay Leno's show. Carson did, however, appear twice on rival late night talk show Late Show with David Letterman (1993) (in a walk-on appearance soon after Letterman's show debuted, and later in a filmed sketch). In the years following Carson's "Tonight Show" retirement, he reportedly contributed jokes to Letterman's monologues from time to time.

On September 27, 2004, the 50th anniversary of "The Tonight Show"'s debut, NBC announced that 'Conan O'Brien' would take over the show in 2009. Leno was still leading the late-night ratings but O'Brien was promised the show so that he would not leave NBC. NBC did not want to lose Leno either and created The Jay Leno Show (2009), the first nightly network primetime talk show. In 2010, due to poor ratings for both O'Brien and Leno's shows, NBC wanted to move Leno's show into O'Brien timeslot, with O'Brien's "Tonight Show" airing at 12:05 am. O'Brien publicly announced that he would rather leave the show than allow that to happen. NBC and O'Brien reached a settlement to allow him to leave the show seven months into his tenure. Leno returned to "The Tonight Show" in March 2010.

You are writing about Late night comedy hosts as though Arsenio Hall is not in the room. You even mention Conon O'brian in the same sentence as Johnny Carson. Are you crazy!

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Nominate Arsenio Hall's name. He is really funny and he's the first African American to Host a Late NIght Comedy Show.Some people want to see Arsenio Hall's name along side Jay Leno as his show made "the first ever done list" so many times, and still is making history. Why mention Conan O'brian's, the racist's, This name show never be mentioned in the same breath with Johnny Carson as these people are so dissimilar one of really funny. You can mention Arsenio Hall's name he's really funny. He like some of the others work toward a better world.